Accounting Changes - Intra-Entity Transfers (Details) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2017 item	Jun. 30, 2018 USD ($) $ / shares	Jun. 30, 2017 USD ($) $ / shares	Jun. 30, 2018 USD ($) item $ / shares	Jun. 30, 2017 USD ($) $ / shares	Dec. 31, 2017 USD ($)		Jan. 01, 2017 USD ($)
Accounting Changes
Investments and sundry assets		$ 2,518		$ 2,518		$ 2,783	[1]
Prepaid expenses and other current assets		2,443		2,443		1,860	[1],[2]
Deferred tax assets		4,689		4,689		4,862
Retained earnings		157,349		157,349		$ 153,126
Continuing operations provision for (benefit from) income taxes		373	$ 111	(166)	$ (218)
Income from continuing operations		2,402	2,332	4,078	4,085
Net income		$ 2,404	$ 2,331	$ 4,083	$ 4,082
Earnings per share, basic (in dollars per share) | $ / shares		$ 2.63	$ 2.49	$ 4.45	$ 4.35
Earnings per share, diluted (in dollars per share) | $ / shares		$ 2.61	$ 2.48	$ 4.43	$ 4.32
Accounting Standards Update 2016-16, Intra-Entity Transfers of Assets Other Than Inventory
Accounting Changes
Number of transactions within scope of new guidance | item				0
Accounting Standards Update 2016-16, Intra-Entity Transfers of Assets Other Than Inventory | Early adoption
Accounting Changes
Investments and sundry assets								$ (95)
Prepaid expenses and other current assets								(47)
Deferred tax assets								244
Retained earnings								$ 102
Number of transactions within scope of new guidance | item	1
Continuing operations provision for (benefit from) income taxes					$ (582)
Income from continuing operations					582
Net income					$ 582
Earnings per share, basic (in dollars per share) | $ / shares					$ 0.62
Earnings per share, diluted (in dollars per share) | $ / shares					$ 0.62

[1] Recast to conform to current period presentation.

[2] Recast to reflect adoption of the FASB guidance on restricted cash.